Advancement in the thermoelectric performance of bulk SnSe: GGA plus U approach for band gap calculation and strain induced thermal conductivity

The utilization of thermoelectric technology for harnessing electricity from waste heat has received considerable interest in recent years. Nevertheless, it is essential to develop high-performance thermoelectric materials that exhibit outstanding conversion efficiency to satisfy the world's energy needs. Density Functional Theory (DFT) techniques have gained wide spread recognition as computational simulation methods for determining electronic properties within materials science. The Boltzmann transport equation, used in conjunction with DFT, serves as a valuable tool for predicting the thermoelectric characteristics of various materials. In this investigation, we conducted a comprehensive analysis of the thermoelectric properties of SnSe using the Quantum Espresso software. Generalized gradient approximations were used as the exchange-correlation functional, which approximates the exchange and correlation energies between electrons in many-body problems. The investigation of core electrons employed ultrasoft pseudopotentials. Additionally, the Hubbard correction tool was applied for the final calculation of the band gap. The optimized structure used for the investigation of the thermoelectric properties of bulk SnSe was supported by the BoltzTraP code. Thermal conductivity studies were conducted using Slack's equation, which incorporates both elastic and lattice characteristics. The examination focused on assessing the impact of changes in lattice strain on lattice thermal conductivity. Notably, a significant alteration in the thermoelectric figure of merit was observed due to the applied lattice strain.